Optical network employing erbium-doped fiber amplifiers

ABSTRACT

A point-to-multipoint bi-directional wide area telecommunications network employing atmospheric optical communication. The network comprises a primary transceiver unit, a plurality of subscriber transceiver units and an optical router. The primary transceiver unit may send data destined for the subscriber transceiver units through the optical router, and the subscriber transceiver units may send data destined for the primary transceiver unit through the optical router. The primary transceiver unit and optical router communicate by means of light beams which are transmitted through the atmosphere. Similarly, the optical router and the subscriber transceiver units communicate by means of light beams which are transmitted through the atmosphere.

CONTINUATION DATA

This application is a continuation of U.S. patent application Ser. No. 10/055,359 filed on Jan. 22, 2002 now U.S. Pat. No. 6,701,092 entitled “LASER Based Telecommunication Network and Router” which is a continuation of U.S. patent application Ser. No. 09/106,826 filed on Jun. 29, 1998 now U.S. Pat. No. 6,348,986 entitled “Wireless Fiber-Coupled Telecommunication Systems Based on Atmospheric Transmission of Laser Signals” which is a continuation-in-part of U.S. patent application Ser. No. 08/625,725 filed on Mar. 29, 1996 entitled “Point-to-Multipoint Wide Area Telecommunications Network via Atmospheric Laser Transmission Through a Remote Optical Router” which has issued as U.S. Pat. No. 5,786,923.

FIELD OF THE INVENTION

The present invention relates generally to wireless telecommunications networks, and more particularly to a broadband telecommunication system and network which employs atmospheric (i.e. free-space) laser transmission.

DESCRIPTION OF THE RELATED ART

Broadband communications applications such as interactive television, video telephony, video conferencing, video messaging, video on demand, high definition television (HDTV) and high-speed data services require a broadband communications network between and to the various subscribers. The current telecommunications network, referred to as the Public Switched Telephone Network (PSTN) or the plain old telephone system (POTS), is presently the only wired network that is accessible to almost the entire population. This system, although ideally suited and designed for point-to-point transmission and any-to-any connectivity, has become nearly overloaded with the use of voice, fax and data communications.

The PSTN today primarily comprises digital switching systems, and transmission over the local loop is typically by either T1 feeder copper-based systems or fiber optic cable systems. However, the subscriber loop is still primarily copper unshielded twisted pair (UTP) wiring, which has a limited capacity. Therefore, the physical nature of the system is severely bandwidth limited, with data transmissions typically in the 9,600–28,800 bits per second range. Thus, high speed broadband applications cannot feasibly be based on POTS technology.

New hard-wired systems, such as ISDN (Integrated Services Digital Network) and fiber optic networks, offer high speed bi-directional communications available to many individuals. However, ISDN itself may not provide sufficient bandwidth for many broadband communications applications. In addition, ISDN requires that most subscribers be connected with upgraded copper wire. A fiber based network, such as fiber to the curb (FTTC) and fiber to the home (FTTH), requires that new fiber optic cable be run to every subscriber. The cost of implementing a fiber optic network across the United States would be very expensive. Other alternatives for increasing the capacity of existing networks include ADSL (Asymmetric Digital Subscriber Line), SDSL (Symmetric Digital Subscriber Line), and HFC (Hybrid Fiber Coax), among others.

An alternative to hard wired network solutions is a wireless-based solution. Most currently existing methods for wireless telecommunications are based upon broadcast methodology in the electromagnetic spectrum. One example of a wireless broadcast medium is the Direct Broadcast Satellite (DBS) system, such as “DirecTV”. In general, broadcast systems are widespread and numerous. However, available bandwidth is increasingly limited by the sheer volume of subscribers, especially with the rapid growth in the cellular phone market. The result of this “crowding of the bands” is that the wireless electromagnetic systems are unable to meet the voracious need of the public for high speed data communications.

Another method for broadband point-to-point communications employs lasers in a point-to-point system that establishes a single continuous, high-speed, bi-directional, multi-channel, atmospheric connection. Laser based wireless systems have been developed for establishing point-to-point, bi-directional and high speed telecommunications through the atmosphere. The range for such systems is typically 0.5 to 1.2 miles, with some having a range of 4 miles or more. The longest atmospheric communications path achieved with a point-to-point system exceeded 100 miles. These single path systems require a laser and transceiver optics at each end of the connection. The connections are capable of maintaining high speed bi-directional communications in some of the most severe inclement weather conditions. The cost of such systems are typically in the $10,000 to $20,000 dollar range however, making them unsuitable for most home and business use.

Therefore, a wireless, laser based telecommunications system is desired that enables a number of subscribers to share a communications path to a great number of subscribers. A wireless, laser based telecommunications system is further desired which reduces the cost to each subscriber, yet still provides high speed, bi-directional, broadband, wide area telecommunications. A system is desired which does not require huge installation costs of ISDN and fiber optics, and which does not require any of the electromagnetic broadcast bands of the mobile communication systems. Such a network could be employed in a wide variety of applications such as telephony, data communications such as the Internet, teleconferencing, radio broadcast, and various television applications such as cable television, HDTV and interactive TV.

SUMMARY OF THE INVENTION

The present invention comprises a point-to-multipoint bi-directional wide area telecommunications network employing atmospheric optical communication. The network comprises a primary transceiver unit, an optical router, and a plurality of subscriber transceiver units. The primary transceiver unit generates a first light beam which includes first modulated data. The optical router receives the first light beam and demodulates the first data. The optical router modulates the first data onto a second light beam and transmits the second light beam to the subscriber transceiver units. The optical router demodulates, modulates and transmits to each of the subscriber transceiver units in a time-multiplexed fashion.

The subscriber transceiver units receive the second light beam and demodulate the first data. Each subscriber transceiver unit comprises an optical antenna or other optical receiver/transmitter. The optical antenna is preferably coupled to an input/output device such as a set-top box or display system, e.g., a computer or television, by a fiber optic cable.

In the other direction, the subscriber transceiver units atmospherically transmit a third light beam which includes second modulated data to the optical router. The optical router demodulates the second data, modulates the second data on a fourth light beam, and transmits the fourth light beam to the primary transceiver unit. The primary transceiver unit receives and demodulates the second data. The optical router demodulates, modulates and transmits to each of the subscriber transceiver units in a time-multiplexed fashion. Thereby, bi-directional communication channels between the primary transceiver unit and the plurality of subscriber transceiver units are established for transferring data in each direction.

The preferred embodiment of the optical router comprises a secondary transceiver unit, a plurality of transceiver modules and an electronic router for routing data between the secondary transceiver unit and the plurality of transceiver modules to establish the communication channels between the primary transceiver unit and the plurality of subscriber transceiver units. The secondary transceiver unit transceives light beams including data with the primary transceiver unit and the transceiver modules transceives light beams including data with the subscriber transceiver units. The transceiver modules comprise an X-Y beam deflector for deflecting the light beams to a portion of the subscriber transceiver units in a time-multiplexed fashion.

In an alternate embodiment of the optical router, the optical router simply redirects the light beams between the primary transceiver unit and the subscriber transceiver units in a time-multiplexed fashion rather than demodulating and remodulating the data. The alternate optical router employs a mirror and lens set to redirect the light beams.

Therefore, the present invention comprises a laser-based atmospheric communication network which provides broadband bi-directional communications to a plurality of subscribers. The present invention provides a bi-directional broadband optical communication network with significantly reduced infrastructure costs. A network of such networks comprising multiple optical routers and multiple primary transceiver units is further contemplated by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which:

FIG. 1 illustrates a point-to-multipoint wide-area telecommunications network using atmospheric laser transmission according to the present invention;

FIG. 2 illustrates the overlapping coverage achieved by the incorporation of multiple optical routers in the network of FIG. 1;

FIG. 3 illustrates a point-to-multipoint wide area telecommunications network using atmospheric laser transmission according to an alternate embodiment of the present invention;

FIG. 4 illustrates the preferred embodiment of the optical router in the network of FIG. 1;

FIG. 5 is a plan view of one of the transceiver modules of FIG. 4;

FIG. 6 is a block diagram of the optical router of FIG. 4, including a detailed block diagram of the secondary transceiver unit;

FIG. 7 illustrates the optical router in the network of FIG. 3;

FIG. 8 illustrates the primary transceiver unit of FIGS. 1 and 3;

FIG. 9 illustrates a subscriber transceiver unit of FIGS. 1 and 3; and

FIG. 10 is a block diagram of a portion of an alternate embodiment of the subscriber transceiver unit of FIG. 9.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Incorporation by Reference

U.S. patent application Ser. No. 09/106,826 filed on Jun. 29, 1998 entitled “Wireless Fiber-Coupled Telecommunication Systems Based on Atmospheric Transmission of Laser Signals is hereby incorporated by reference in its entirety.

U.S. patent application Ser. No. 08/625,725 filed on Mar. 29, 1996 entitled “Point-to-Multipoint Wide Area Telecommunications Network via Atmospheric Laser Transmission Through a Remote Optical Router” which has issued as U.S. Pat. No. 5,786,923 is hereby incorporated by reference in its entirety.

For general information on broadband telecommunications and optical data communications, please see Lee, Kang and Lee, Broadband Telecommunications Technology, Artech House, 1993 which is hereby incorporated by reference in its entirety. Also please see Davis, Carome, Weik, Ezekiel, and Einzig, Fiber Optic Sensor Technology Handbook, Optical Technologies Incorporated, 1982, 1986, Herndon, Virginia, which is hereby incorporated by reference in its entirety.

A Network with an Optical Router and a Primary Transceiver

Referring now to FIG. 1, a point-to-multipoint wide-area telecommunications network 3100 using atmospheric light beam or laser transmission according to the present invention is shown. The network 3100 preferably comprises a primary transceiver unit 3120, an optical router 3110 and a plurality of subscriber transceiver units 3130A–3130N (referred to collectively as 3130). In an alternate embodiment, the network 3100 comprises only the optical router 3110 and the plurality of subscriber transceiver units. The present invention provides a broadband bi-directional communication network with reduced infrastructure costs, i.e., no cable or fiber is required to be laid in the subscriber loop, i.e., to the subscribers.

According to the preferred embodiment of network 3100, the subscriber transceiver units are located at subscriber premises, such as homes or businesses. The optical router 3110 is located in the vicinity of the subscriber transceiver units 3130, and the optical router optically communicates with the subscriber units 3130. The optical router 3110 has an associated range of accessibility, wherein the optical router 3110 is capable of communicating with subscriber transceiver units located within a circular area around the optical router 3110. In the preferred embodiment of optical router 3110, the range of accessibility is approximately between 2000 and 4000 feet. It is contemplated, however, that optical router 3110 may be configured with larger or smaller ranges of accessibility. Each of the subscriber transceiver units 3130 is positioned in a line of sight path relative to the optical router 3110.

The optical router 3110 is positioned in a line of sight path relative to the primary transceiver unit 3120. The optical router 3110 is preferably mounted on, for example, a pole, building, or other structure approximately 75 feet above ground level. Preferably the distance between the primary transceiver unit 3120 and the optical router 3110 is approximately in the range from one half to ten miles. It is contemplated, however, that larger or smaller distances may exist between the optical router 3110 and the primary transceiver unit 3120 of network 3100

The primary transceiver unit 3120 generates a first light beam 3140 and atmospherically transmits the first light beam 3140 to the optical router 3110. In the preferred embodiment, the term “light beam” is intended to encompass any of various types of light transmission, including lasers, a super-fluorescent light source, or other coherent and/or non-coherent light or optical transmission.

The primary transceiver unit 3120 modulates data on the first light beam 3140 before transmitting the first light beam 3140 to the optical router 3110. Data may be modulated on the first light beam using any of various techniques, including amplitude and/or frequency modulation techniques, as is well known in the art.

The optical router 3110 atmospherically receives the first light beam 3140 including the data sent by the primary transceiver unit 3120 and demodulates the data, then modulates the data on and atmospherically transmits a second light beam 3845A–3845N (referred to collectively as 3845) to the subscriber transceiver units 3130. The second light beam 3845 contains at least a portion of the data sent by the primary transceiver unit 120. The subscriber transceiver units 3130 atmospherically receive the second light beam 3845 and demodulate the data sent by the primary transceiver unit 3120 from the second light beam 3845. The present invention distinguishes among different users, i.e., shares the communication bandwidth, using techniques such as time-division multiple access (TDMA) or frequency-division multiple access (FDMA). The present invention may also use code-division multiple access (CDMA) techniques.

The subscriber transceiver units 3130 atmospherically transmit a third light beam 3855A–3855N (referred to collectively as 3855) to the optical router 3110. The subscriber transceiver units 3130 modulate data on the third light beam 3855 and then transmit the third light beam 3855 to the optical router 3110. The optical router 3110 atmospherically receives the third light beam 3855 including the data sent by the subscriber transceiver units 3130 and demodulates the data, then modulates the data on and atmospherically transmits a fourth light beam 3150 to the primary transceiver unit 3120. The primary transceiver unit 3120 receives the fourth light beam 3150 and demodulates the data sent by the subscriber transceiver units 3130 from the fourth light beam 3150.

The optical router 3110 routes data between the primary transceiver unit 3120 and each of the subscriber transceiver units 3130 thus establishing channels of communication, that is, subscriber channels, on the light beams between the primary transceiver unit 3120 and the subscriber transceiver units 3130. Preferably the optical router 3110 establishes subscriber channels in a time-multiplexed fashion. During a first time-period the optical router 3110 establishes a first set of one or more subscriber channels between the primary transceiver unit 3120 and a first set of one or more subscriber transceiver units 3130. Next, the optical router 3110 establishes a second set of subscriber channels between the primary transceiver unit 3120 and a second set of subscriber transceiver units 3130 during a second time-period. The optical router 3110 proceeds in this manner, establishing a two-way or bi-directional subscriber channel with each of the subscriber transceiver units 3130 in the range of accessibility of the optical router 3110.

One embodiment of network 3100 contemplates any or all of the first light beam 3140, second light beam 3845, third light beam 3855, and fourth light beam 3150, comprising a plurality of different wavelengths, wherein data is modulated on each wavelength of the light beams, thereby advantageously increasing the bandwidth of the subscriber channels.

The network of the present invention may support a large number of subscribers. One embodiment contemplates on the order of 1000 subscriber transceiver units supported by a single optical router.

In an alternative embodiment of network 3100, primary transceiver unit 3120 receives the first light beam 3140 from another transceiver (not shown) and optically redirects the first light beam 3140 to optical router 3110. Conversely, primary transceiver 3120 optically redirects the fourth light beam 3150 from optical router 3110 to the other transceiver.

In a second alternative embodiment of network 3100, primary transceiver unit 3120 receives a source light beam from another transceiver (not shown), and demodulates data from the source light beam which then becomes the data source for modulating the first light beam. Conversely, primary transceiver unit 3120 demodulates data sent by the subscriber transceiver units from the fourth light beam 3150. The demodulated data is modulated onto a return light beam which is atmospherically transmitted to the other transceiver.

In a third alternative embodiment of network 3100, optical router 3110 communicates with another transceiver (not shown). Optical router 3110 atmospherically transmits the fourth light beam 3150 to the other transceiver for demodulation, and receives the first light beam 3140 from the other transceiver.

Thus, it may be readily observed that the elements recited above form a wireless point-to-multipoint wide-area telecommunications network. By establishing subscriber communications channels in a multiplexed manner using atmospherically transmitted light beams, the present invention advantageously provides a telecommunications network which has the potential to be much less expensive than current wired networks which rely on copper wire and/or optical fiber.

Additionally, the present invention advantageously provides a much less expensive telecommunications network than a network which employs an array of point-to-point atmospherically transmitted light beams.

Further, by employing light beams as the communications path, the present invention advantageously avoids the costs associated with licensing and purchasing bands in the radio spectrum.

Finally, the present invention advantageously provides a communications network which consumes much less power than a system which employs an angularly dispersed light beam.

In the preferred embodiment of network 3100, the primary transceiver unit 3120 communicates control information to the optical router 3110 and subscriber transceiver units 3130. The control information for the optical router 3110 contains information about the angular location of the subscriber transceiver units 3130. The control information also contains timing information to instruct the optical router 3110 regarding multiplexing of the light beams and thus establishing the subscriber communications channels. The control information for the subscriber transceiver units 3130 contains timing information instructing the subscriber transceiver units 3130 about when to transmit the third light beam 3855 to the optical router 3110. The primary transceiver unit 3120 transmits the first light beam 3140 and receives the fourth light beam 3150 cooperatively according to the control information which the primary transceiver unit 3120 communicates to the optical router 3110 and subscriber transceiver units 3130.

In the preferred embodiment of network 3100, the primary transceiver unit 3120 includes a master clock and computes timing control information based upon at least a plurality of the following factors: the data packet size, the local speed of light, the number of subscribers, the distance between the primary transceiver unit and the optical router, the distance between the optical router and the respective subscriber transceiver unit, the processing time of the subscriber transceiver units, the time associated with the electronic router (discussed below), and the switching speed of the X-Y beam deflectors (discussed below).

In the preferred embodiment of network 3100, the first light beam 3140 and the fourth light beam 3150 are substantially collinear as are the second light beam 3845 and third light beam 3855. The collinear light beam embodiment advantageously allows many of the optical components of the primary transceiver unit, optical router and subscriber transceiver units to be shared by the light beams. In this embodiment, the first light beam 3140 and the fourth light beam 3150 have different frequencies or polarities as do the second light beam 3845 and third light beam 3855 to advantageously avoid cross-talk between the two light beams. In an alternate embodiment, the first light beam 3140 and fourth light beam 3150 are in close proximity but not collinear as are the second light beam 3845 and third light beam 3855.

Referring now to FIG. 2, a network comprising a plurality of optical routers is shown. Each optical router has an associated range of accessibility. In one embodiment of the present invention, the optical routers are spatially located such that the accessibility ranges of some of the optical routers overlap. That is, more than one optical router is able to service a given subscriber. FIG. 2 shows various regions of coverage and indicates the number of optical routers which may service a subscriber located in the region.

In one embodiment of network 3100, if a subscriber transceiver unit detects a loss of reception of the first light beam, the subscriber transceiver unit searches for another optical router by which to receive service. By providing overlapping coverage of a given subscriber by multiple optical routers, the present invention advantageously provides an element of redundancy and hence more reliable operation.

In FIG. 2, three optical routers are shown. However, the present invention is not limited in the number of optical routers which may be serviced by a given primary transceiver unit 3120, nor the number of optical routers which may service a given subscriber transceiver unit 3130.

In one embodiment of network 3100, the primary transceiver unit 3120 comprises a plurality of light sources to generate a plurality of first light beams to transmit to a plurality of optical routers. In another embodiment of network 3100, the primary transceiver unit 3120 comprises a single light source to generate a single light beam, and the primary transceiver unit 3120 is configured to split the light beam generated by the single light source into multiple first light beams which are transmitted to a plurality of optical routers. In both embodiments the primary transceiver unit 3120 modulates subscriber data on each first light beams.

Alternate Embodiments

Referring now to FIG. 3, an alternate embodiment of the network 3100 of FIG. 1 is shown. The embodiment of FIG. 3 is similar to the embodiment of FIG. 1, and corresponding elements are numbered identically for simplicity and clarity. The optical router 3110 of FIG. 3 corresponds to the alternate embodiment of the optical router 3110 shown in FIG. 7 and described below. In the alternate embodiment the optical router 3110 redirects the light beam from the primary transceiver unit 3120 to the subscriber transceiver units 3130 and redirects the light beams from the subscriber transceiver units 3130 to the primary transceiver unit 3120 rather than demodulating the data and re-modulating it. The optical router 3110 receives the first light beam 3140 and redirects the first light beam 3140 to the subscriber transceiver units 3130. The subscriber transceiver units 3130 receive the first light beam 3140 and demodulate the data sent by the primary transceiver unit 3120 from the first light beam 3140. The present embodiment distinguishes among different users, i.e., shares the communication bandwidth, using techniques such as time division multiple access (TDMA) or frequency division multiple access (FDMA). The present embodiment may also use code division multiple access (CDMA) techniques.

The subscriber transceiver units 3130 atmospherically transmit a second light beam 3150A–3150N (referred to collectively as 3150) to the optical router 3110. The subscriber transceiver units 3130 modulate data on the second light beam 3150 and then transmit the second light beam 3150 to the optical router 3110. The optical router 3110 receives the second light beam 3150 and redirects the second light beam 3150 to the primary transceiver unit 3120. The primary transceiver unit 3120 receives the second light beam 3150 and demodulates the data sent by the subscriber transceiver units 3130 from the second light beam 3150. Alternatively, the optical router 3110 and/or the primary transceiver unit 3120 provide the second light beam 3150 to another transceiver (not shown) for demodulation, wherein this other transceiver is in communication with the primary transceiver unit 3120.

The optical router 3110 redirects the first and second light beams between the primary transceiver unit 3120 and each of the subscriber transceiver units 3130 during different time periods, that is, in a time-multiplexed manner. In other words, the optical router 3110 establishes channels of communication comprising the light beams between the primary transceiver unit 3120 and the subscriber transceiver units 3130 in distinct time slices. Thus, during a first time period the optical router 3110 establishes a first subscriber channel by redirecting the first light beam 3140 from the primary transceiver unit 3120 to a first subscriber transceiver unit 3130 and redirecting the second light beam 3150 from the first subscriber transceiver unit 3130 to the primary transceiver unit 3120. Next, the optical router 3110 establishes a second subscriber channel between the primary transceiver unit 3120 and a second subscriber transceiver unit 3130 during a second time period. The optical router 3110 proceeds in this manner, establishing a two-way or bi-directional subscriber channel with each of the subscriber transceiver units 3130 in the range of accessibility of the optical router 3110.

An alternate embodiment of the network 3100 contemplates an alternate multiplexing scheme wherein the primary transceiver unit 3120 is configured to generate and/or transmit a first light beam 3140 which comprises a plurality of different wavelengths which correspond to the subscribers. The optical router 3110 receives the first light beam and provides each of the wavelength portions to the respective subscriber transceiver units. In this embodiment, the optical router 3110 includes a grating, such as a diffraction grating, which separates the different frequency or spectra and provides the different wavelength portions to the respective subscribers. Additionally, each subscriber transceiver unit is configured to generate a second light beam of one or more respective unique wavelengths. The optical router 3110 redirects the respective wavelength light beams of the first and second light beams between the primary transceiver unit 3120 and respective subscriber transceiver units 3130, that is, in a frequency-multiplexed manner. Alternately stated, the optical router 3110 establishes subscriber channels of communication on the light beams between the primary transceiver unit 3120 and the subscriber transceiver units 3130 based upon different wavelength portions of a light beam. Thus, the optical router 3110 establishes a first subscriber channel by redirecting a first wavelength portion of the first light beam from the primary transceiver unit 3120 to a first subscriber transceiver unit 3130 and redirecting the second light beam 3150 comprising the first wavelength from the first subscriber transceiver unit 3130 to the primary transceiver unit 3120. Simultaneously, the optical router 3110 establishes a second subscriber channel between the primary transceiver unit 3120 and a second subscriber transceiver unit 3130 using a second wavelength portion of the first light beam 3140 and a second light beam 3150 comprising the second wavelength. The optical router 3110 operates in this manner, establishing a subscriber channel with subscriber transceiver units 3130 in the range of accessibility of the optical router 3110. By employing multiple wavelength light beams and FDMA techniques, the invention advantageously increases the bandwidth available to the subscribers.

Another alternate multiplexing embodiment is contemplated in which the optical router 3110 establishes subscriber communication channels in a combined time-multiplexed and frequency-multiplexed manner. A subscriber requiring increased data bandwidth employs a subscriber transceiver unit configured to receive multiple light beams of differing wavelengths and/or multiple time-slots, thereby multiplying the bandwidth available to the subscriber. In another embodiment, the present invention employs code division multiple access (CDMA) techniques using bipolar codes.

The present invention contemplates an alternate embodiment of the network 3100 comprising unidirectional data transmission, that is, broadcast or point-to-multipoint data communication only from the primary transceiver unit 3120 and/or optical router 3110 to the subscriber transceiver units 3130. In this embodiment, the subscriber transceiver units 3130 do not generate light beams back through the optical router 3110 to the primary transceiver unit 3120. Other aspects of this alternate embodiment are as described above in the preferred embodiment of FIG. 1 and the alternate embodiment of FIG. 3. This alternate embodiment is contemplated as an advantageous alternative to current implementations of broadcast television, particularly high definition television, or cable television, for example. Thus this embodiment may comprise a pure broadcast (one-way) network. Alternatively, the network 3100 may use a different return path from the subscriber units 3130 to the primary transceiver unit 3120, such as an analog modem (POTS) or ISDN.

The present invention further contemplates an alternate embodiment of the network 3100 in which the primary transceiver unit 3120 essentially resides in the same location as the optical router 3110. Alternately stated, the primary transceiver unit 3120 and the optical router 3110 are essentially combined into a single unit. In this embodiment the light source of the primary transceiver unit 3120 transmits only a few inches or feet into the optical router 3110. Various elements of the primary transceiver unit 3120 and optical router 3110 may be eliminated or combined in such an embodiment. In this embodiment, fiber optic cable may be used to transfer the light beam directly to the optical router 3110, and thus a separate primary transceiver unit 3120 is not needed.

The Optical Router

Referring now to FIG. 4, the preferred embodiment of the optical router 3110 in the network 3100 (of FIG. 1) is shown. The optical router 3110 comprises a secondary transceiver unit 3700 coupled to a plurality of transceiver modules 3800A–3800M (referred to collectively as 3800) by an electronic router 3790. The transceiver modules 3800 are coupled to a circular backplane 3889. The electronic router 3790 is coupled to the transceiver modules 3800 through the backplane 3889.

Transceiver module 3800A (representative of the transceiver modules 3800) has a backplane connector 3888 which connects the transceiver module 3800A to the backplane. The transceiver module 3800A is configured to transmit the second light beam 3845 to and receive the third light beam 3855 from a portion of the subscriber transceiver units 3130, namely those subscriber transceiver units 3130 within a portion of the circular area around the optical router 3110. The transceiver modules 3800 collectively provide the optical router 3110 with a 360 degree range of accessibility to the subscriber transceiver units 3130.

A beam deflector control system 3795 is coupled through the backplane 3889 to the transceiver modules 3800 for controlling the deflection of the second light beam 3845 and third light beam 3855 by the transceiver modules 3800. The beam deflector control system 3795 is also coupled to the electronic router 3790 and receives beam deflector control information from the primary transceiver unit 3120 through the electronic router 3790.

The electronic router 3790 receives routing control information from the primary transceiver unit 3120. The routing control information regards the routing of data sent by the primary transceiver unit 3120 from the secondary transceiver unit 3700 to the various transceiver modules 3800 for atmospheric transmission to the subscriber transceiver units 3130. Conversely, the routing control information regards the routing of data sent by the subscriber transceiver units 3130 from the various transceiver modules 3800 to the secondary transceiver unit 700 for atmospheric transmission to the primary transceiver unit 3120.

The secondary transceiver unit 3700 atmospherically receives the first light beam 3140 including the data sent by the primary transceiver unit 3120 and demodulates the data. The secondary transceiver unit 3700 communicates the data sent by the primary transceiver unit 3120 to the electronic router 3790. The electronic router 3790 routes the data from the secondary transceiver unit 3700 to the appropriate one of the transceiver modules 3800. For illustration purposes let us assume transceiver module 3800A is the appropriate transceiver module 3800. The transceiver module 3800A receives the data and modulates the data onto the second light beam 3845 which is atmospherically transmitted to the appropriate subscriber transceiver unit 3130A.

Conversely, the transceiver module 3800A receives the third light beam 3855 including data from the subscriber transceiver unit 3130 and demodulates the data. The transceiver module 3800A communicates the data sent by the subscriber transceiver unit 3130A to the electronic router 3790. The electronic router 3790 routes the data from the transceiver module 3800A to the secondary transceiver unit 3700. The secondary transceiver unit 700 modulates the data sent by the subscriber transceiver unit 3130A onto the fourth light beam 3150 and atmospherically transmits the fourth light beam 3150 including the data sent by the subscriber transceiver unit 3130A to the primary transceiver unit 3120.

FIG. 5

Referring now to FIG. 5, a plan view of the transceiver module 3800A of the optical router 3110 of FIG. 4 is shown. The transceiver module 3800A comprises a light source 3862 configured to generate the second light beam 3845. A beam modulator 3864 receives data which was sent by the primary transceiver unit 3120 from the electronic router 3790 through the backplane connector 3888 and modulates the data onto the second light beam 3845. The second light beam 3845 is deflected by an X-Y beam deflector 3840 to the subscriber transceiver unit 3130A.

Preferably the X-Y beam deflector 3840 is a galvanometer mirror pair. Galvanometer mirrors are well known, particularly in the art of laser printer technology and the art of laser light shows. Alternatively the X-Y beam deflector 3840 is an acousto-optic or solid state beam deflector. The optical router 3110 light source 3862 preferably comprises one or more continuous wave or pulsed beam lasers as are well known in the art, such as gas, solid state or diode lasers. The beam modulator 3864 preferably comprises an electro-optic cell. Alternatively, the beam modulator 3864 is a bulk type modulator. The light source and beam modulator configuration is indicative of those well known in fiber optic communication link transmission systems. However, the laser power output is typically significantly greater than those used in fiber optic systems.

While the X-Y beam deflector 3840 deflects the second light beam 3845 to the subscriber transceiver unit 3130A the X-Y beam deflector 3840 simultaneously deflects the third light beam 3855 from the subscriber transceiver unit 3130A to a beam splitter 3880. The beam splitter 3880 splits a relatively large portion of the third light beam 3855 to a beam demodulator 3872 which receives the third light beam 3855 and demodulates data sent by the subscriber transceiver unit 3130A from the third light beam 3855. The beam demodulator 3872 communicates the data through the backplane connector 3888 to the electronic router 3790. The beam demodulator 3872 preferably comprises a photo-diode as is common in the art.

During a first time period, the X-Y beam deflector 3840 deflects the second light beam 3845 from the light source 3862 to a first subscriber transceiver unit 3130A and deflects the third light beam 3855 from the first subscriber transceiver unit 3130A to the beam demodulator 3872. Hence, the transceiver module 3800A establishes a bi-directional communications channel using the second and third light beams between the transceiver module 3800A and the first subscriber transceiver unit 3130A for a first period of time. Hence, the bi-directional communications channel between the transceiver module 3800A and the first subscriber transceiver unit 3130A comprises a portion of the subscriber channel described above between the primary transceiver unit 3120 and the subscriber transceiver unit 3130A. During subsequent periods of time the X-Y beam deflector 3840 deflects the second and third light beams to and from other subscriber transceiver units 3130 in a time-multiplexed manner.

Each of the transceiver modules 3800 establishes bi-directional communication channels as just described between the given transceiver module and the portion of the subscriber transceiver units 3130 accessible by the given transceiver module in a time-multiplexed fashion and simultaneously with the other transceiver modules. In this manner, a portion of a wireless point-to-multipoint bi-directional wide area telecommunications network is advantageously formed between the optical router 3110 and the subscriber transceiver units 3130.

The beam splitter 3880 splits a relatively small portion of the third light beam 3855 to a beam alignment detector 3852 which receives the split portion of the third light beam 3855 and detects misalignment or wander of the third light beam 3855 from the subscriber transceiver unit 3130A which may occur and stores the beam stabilization information. The beam alignment detector 3852 communicates the beam stabilization information through the backplane 888 via the electronic router 3790 to the secondary transceiver unit 3700. The secondary transceiver unit 3700 transmits the beam stabilization information to the primary transceiver unit 3120. The primary transceiver unit 3120 communicates the beam stabilization information to the given subscriber transceiver unit so that the subscriber transceiver unit can adjust the beam for misalignment or wander appropriately. Atmospheric turbulence and density variations along the atmospheric path between the subscriber transceiver unit 3130A and the optical router 3110 may account for misalignment of the third light beam 3855 on the X-Y beam deflector 3840 of the transceiver module 3800A. Likewise, events such as ground shifting or tower sway may cause the positions of the subscriber transceiver unit 3130A or optical router 3110 relative to each other to change.

FIG. 6

Referring now to FIG. 6, a block diagram of the optical router 3110 of FIG. 4 is shown including a detailed block diagram of the secondary transceiver unit 3700. A transceiver module 300A is coupled to the electronic router 3790 through the backplane 3889. The electronic router 3790 is also coupled to the other transceiver modules 3800 (not shown). The electronic router 3790 is coupled to the beam deflector control system 3795 and to the secondary transceiver unit 3700.

The secondary transceiver unit 3700 comprises an optical antenna 3210 which receives the first light beam 3140 from the primary transceiver unit 3120. The optical antenna 3210 also transmits the fourth light beam 3150 to the primary transceiver unit 3120. The optical antenna 3210 preferably comprises an optical system with a conic mirror, which is well known in the art. Alternatively the optical antenna 3210 is a collecting lens system which is also well known in the art. The optical antenna 3210 and associated optics converge and re-collimate the incoming first light beam 3140 to a relatively small diameter, preferably in the range of 1 to 3 millimeters. Conversely, the optical antenna 3210 receives a relatively small diameter fourth light beam 3150 generated by a light source 3362 and expands and re-collimates the fourth light beam 3150 for atmospheric transmission to the primary transceiver unit 3120.

The optical antenna 3210 atmospherically receives the first light beam 3140 including the data sent by the primary transceiver unit 3120 (of FIG. 1) from the primary transceiver unit 3120 and directs the first light beam 3140 to a beam demodulator 3372. The beam demodulator 3372 demodulates the data sent by the primary transceiver unit 3120 from the first light beam 3140 and communicates the data to the electronic router 3790. The data sent by the primary transceiver unit 3120 comprises subscriber data as well as control data. The control data comprises routing control information for the electronic router 3790 as well as timing control information and angular position control information of the subscriber transceiver units 3130 for the beam deflector control system 3795. The electronic router 3790 uses the routing control information to route the subscriber data to the appropriate transceiver modules 3800. The electronic router 3790 communicates the timing control information and the angular position control information to the beam deflector control system 3795. The beam demodulator 3372 preferably comprises a photo-diode as is common in the art.

The light source 3362 generates the fourth light beam 3150. The electronic router 3790 routes the data sent by the subscriber transceiver units 3130 from the transceiver modules 3800 to a beam modulator 3364. The beam modulator 3364 modulates the data sent by the subscriber transceiver units 3130 onto the fourth light beam 3150 for transmission to the optical antenna 3210 and on to the primary transceiver unit 3120.

The light source 3362 preferably comprises one or more continuous wave or pulsed beam lasers as are well known in the art, such as gas, solid state or diode lasers. The beam modulator 3364 preferably comprises an electro-optic cell. Alternatively, the beam modulator 3364 is a bulk type modulator. The light source and beam modulator configuration is indicative of those well known in fiber optic communication link transmission systems. However, the laser power output is typically significantly greater than those used in fiber optic systems.

As the first light beam 3140 passes from the optical antenna 3210 to the beam demodulator 3372 the first light beam 3140 is directed toward the beam demodulator 3372 by a beam separator 3380. Conversely, as the fourth light beam 3150 passes from the light source 3362 to the optical antenna 3210 the fourth light beam 3150 passes through the beam separator 3380.

The X-Y beam deflector 3840 is coupled through the backplane 3889 to the beam deflector control system 3795. The beam deflector control system 3795 controls the switching of the X-Y beam deflector 3840 to deflect the second light beam 3845 and third light beam 3855 to and from the desired subscriber transceiver unit 3130 at the desired time. Thus in a time-multiplexed fashion the beam deflector control system controls the establishing of the portion of the subscriber channels between the subscriber transceiver units 3130 and the transceiver modules 3800.

Preferably, the beam deflector control system 3795 receives control information from the primary transceiver unit 3120 to control the X-Y beam deflector 3840. The control information for the beam deflector control system 3795 contains information about the angular location of the subscriber transceiver units 3130. The beam deflector control system 3795 uses the subscriber transceiver unit angular location information to determine the desired deflection angles of the X-Y beam deflector 3840.

As mentioned in the discussion of FIG. 1, the primary transceiver unit 3120 also preferably transmits multiplexing control information to the optical router 3110 and to the subscriber transceiver units 3130. The primary transceiver unit 3120 transmits the control information for one or more subscriber channels prior to transmitting the subscriber data packets associated with the one or more subscriber channels. The multiplexing information is timing information used by the beam deflector control system 3795 to control the X-Y beam deflector 3840 regarding when to deflect the second and third light beams to and from a given subscriber transceiver unit 3130.

The subscriber transceiver unit transmits the third light beam 3855 containing data for the primary transceiver unit 3120 to the optical router 3110 at a time determined by the primary transceiver unit 3120. Correspondingly, the transceiver module servicing the subscriber transceiver unit transmits the second light beam with the data modulated for the subscriber transceiver unit to arrive at the X-Y beam deflector at substantially the same time as the third light beam 3855 containing data from the first subscriber arrives at the optical router 3110. The primary transceiver unit 3120 transmits the first light beam 3140 containing data for the subscriber transceiver unit to arrive at the optical router 3110 at a time such that the data may be demodulated, routed, modulated on the second light beam 3845 and the second light beam 3845 transmitted to arrive at the X-Y beam deflector 3840 at substantially the same time as the third light beam 3855 containing data from the first subscriber arrives at the optical router 3110.

By employing optical components to converge and re-collimate the light beams as described previously, the internal components of the optical router 3110, such as the beam deflector, advantageously operate on relatively narrow light beams. This improves the accuracy of beam redirection. Conversely, by employing optical components to expand and re-collimate the light beams as described previously, the light beams traveling through the atmosphere between network elements are advantageously relatively wide light beams. This improves the reception characteristics of the light beams as they are received by the network components.

The optical router 3110 further comprises an active optics control system 3350, such as are well known, particularly in the defense industry. The active optics control system 3350 provides stabilization of the first light beam 3140 on the optical antenna 3210 of the optical router 3110 and of the fourth light beam 3150 on the optical antenna 3710 (of FIG. 8) of the primary transceiver unit 3120. As the first light beam 3140 travels from the optical antenna 3210 toward the beam demodulator 3372, a small portion of the first light beam 3140 is split by a beam separator 3380 and redirected to a beam alignment detector 3352. The beam alignment detector 3352 detects misalignment or wander in the first light beam 3140 which may occur and stores the beam stabilization information. Atmospheric turbulence and density variations along the atmospheric path between the primary transceiver unit 3120 and the optical router 3110 may account for misalignment of the first light beam 3140 on the optical router 3110. Likewise, events such as ground shifting or tower sway may cause the positions of the primary transceiver unit 3120 or optical router 3110 relative to each other to change.

The active optics control system 3350 communicates the beam stabilization information to the electronic router 3790 which in turn communicates the beam stabilization information to the beam modulator 3364. The beam modulator 3364 modulates the beam stabilization information data onto the fourth light beam 3150 during a designated time period for atmospheric transmission to the primary transceiver unit 3120. The primary transceiver unit 3120 demodulates the beam stabilization information data from the fourth light beam 3150 and uses the beam stabilization information to make corrections and stabilize the first light beam 3140 on the optical router 3110.

Additionally, the active optics control system 3350 uses the beam misalignment information to control a beam adjuster 3220, positioned between the optical antenna 3210 and the beam splitter 3230, to adjust the first light beam 3140 optimally into the beam demodulator 3372.

As previously mentioned the primary transceiver unit 3120 communicates control information to the optical router 3110. The control information further comprises beam stabilization information. The active optics control system 3350 uses the beam stabilization information from the primary transceiver unit 3120 to control the optical antenna 3210 and beam adjuster 3220 to make corrections and stabilize the fourth light beam 3150 on the primary transceiver unit 3120.

Preferably the beam separator 3380 is a dichroic mirror. Alternatively, the first light beam 3140 and fourth light beam 3150 are orthogonally polarized and the beam separator 3380 is a polarization separator.

In the preferred embodiment of the invention, the optical router 3110 periodically polls the subscriber transceiver units 3130 by allocating a communication channel to each of the subscriber transceiver units 3130 within the range of accessibility of the optical router 3110. However, the optical router 3110 may lose reception of the third light beam 3855 from a given subscriber transceiver unit for a significant period of time. The most common cause of the reception loss is the subscriber transceiver unit being powered off. When the optical router 3110 detects reception loss, the optical router 3110 preferably and advantageously polls the powered-off subscriber less frequently than subscriber transceiver units which are actively transmitting a third light beam 3855 to the optical router 3110.

Alternate Embodiment

Referring now to FIG. 7, an alternate embodiment of the optical router 3110 in the network 3100 (of FIG. 3) is shown. The optical router 3110 comprises an optical antenna 3210 which receives the first light beam 3140 from the primary transceiver unit 3120. The optical antenna 3210 also transmits the second light beam 3150 received from a subscriber transceiver unit to the primary transceiver unit 3120. The optical antenna 3210 preferably comprises an optical system with a conic mirror, which is well known in the art. In an alternate embodiment the optical antenna 3210 is a collecting lens system which is also well known in the art. The optical antenna 3210 and associated optics converge and re-collimate the incoming first light beam 3140 to a relatively small diameter, preferably in the range of 1 to 3 millimeters. Conversely, the optical antenna 3210 receives a relatively small diameter second light beam 3150 received from internal components of the optical router 3110 and expands and re-collimates the second light beam 3150 for atmospheric transmission to the primary transceiver unit 3120.

The optical antenna 3210 receives the first light beam 3140 from the primary transceiver unit 3120 (of FIG. 3) and directs the first light beam 3140 to an X-Y beam deflector 3240. The beam deflector 3240 receives the first light beam 3140 and deflects the first light beam 3140 toward a mirror 3261. The mirror 3261 reflects the first light beam 3140 to a respective one or more of the subscriber transceiver units 3130 (of FIG. 3). Conversely, the subscriber transceiver units 3130 transmit respective second light beams 3150 to the mirror 3261. The mirror 3261 reflects a received second light beam 3150 to the beam deflector 3240. The beam deflector 3240 deflects the second light beam 3150 to the optical antenna 3210. The optical antenna 3210 receives the second light beam 3150 and transmits the second light beam 3150 to the primary transceiver unit 3120.

Preferably, during a first time period, the beam deflector 3240 deflects the first light beam 3140 from the optical antenna 3210 to a location on the mirror 3261 and deflects the second light beam 3150 from substantially the same location on the mirror to the optical antenna 3210. The location on the mirror 3261 is calculated to reflect the first light beam 3140 to a particular subscriber transceiver unit and reflect the second light beam 3150 from the particular subscriber transceiver unit. Hence, the optical router 3110 establishes a bi-directional communications channel using the first and second light beams between the primary transceiver unit 3120 and one of the subscriber transceiver units 3130 for a period of time. During subsequent periods of time the beam deflector 3240 deflects the light beams to other locations on the mirror 3261 in order to establish channels with the other subscriber transceiver units 3130 serviced by the optical router 3110. In this manner, a wireless point-to-multipoint bi-directional wide area telecommunications network is advantageously formed.

The beam deflector 3240 is controlled by a beam deflector control system 3340 coupled to the beam deflector 3240. The beam deflector control system 3340 controls the beam deflector 3240 to deflect the light beams to the desired locations on the mirror 3261 during the desired time. Preferably, the beam deflector control system 3340 receives control information from the primary transceiver unit 3120 to control the beam deflector 3240. The control information for the optical router 3110 contains information about the angular location of the subscriber transceiver units 3130. The beam deflector control system 3340 uses the subscriber transceiver unit angular location information to determine the desired locations on the mirror 3261 used for deflection of the light beams.

As mentioned in the discussion of FIG. 3, the primary transceiver unit 3120 also preferably transmits multiplexing control information to the optical router 3110 and to the subscriber transceiver units 3130. The primary transceiver unit 3120 transmits the control information for one or more subscriber channels prior to transmitting the subscriber data packets associated with the one or more subscriber channels. Preferably, the multiplexing information is timing information used by the beam deflector control system 3340 to control the beam deflector 3240 regarding when to deflect the light beams to and from a particular location on the mirror 3261. A first subscriber transceiver unit 3130 transmits the second light beam 3150 containing data for the primary transceiver unit 3120 to the optical router 3110 at a time determined by the primary transceiver unit 3120. Correspondingly, the primary transceiver unit 3120 transmits the first light beam 3140 containing data for the first subscriber to the optical router 3110 at a time such that the first light beam 3140 containing data for the first subscriber arrives at the optical router 3110 at substantially the same time the second light beam 3150 containing data from the first subscriber arrives at the optical router 3110. Additionally, the beam deflector control system 3340 controls the beam deflector 3240 to redirect the first and second light beams between the primary transceiver unit 3120 and first subscriber transceiver unit 3130 during the time when the first and second light beams are passing through the optical router 3110, as directed by the primary transceiver unit 3120.

Preferably, the X-Y beam deflector 3240 is a galvanometer mirror pair. Galvanometer mirrors are well known, particularly in the art of laser printer technology and the art of laser light shows.

One embodiment contemplates the beam deflector 3240 comprising a plurality of such galvanometer mirror pairs. Each galvanometer mirror pair deflects a different light beam between the mirror 3261 and the optical antenna 3210. The primary transceiver unit 3120 transmits the first light beam 3140 which is comprised of multiple light beams each of a different wavelength, i.e., the first light beam 3140 includes a plurality of different wavelengths. The optical router 3110 splits the first light beam 3140 into respective wavelength portions which are deflected by respective beam deflectors. Conversely, multiple subscriber transceiver units 3130 transmit second light beams 3150 of differing wavelengths which arrive simultaneously at the optical router 3110. The optical router 3110 combines the multiple wavelength second light beams 3150 and transmits the multiple wavelength second light beam 3150 to the primary transceiver unit 3120.

Other embodiments contemplate the beam deflector 3240 comprising one or more acousto-optic or solid state beam deflectors.

Preferably the mirror 3261 is a conical or hemispherical mirror wherein the cone axis is in a vertical orientation, thus providing 360 degree access to subscribers with an elevation aperture covering the access area to a range of approximately between 2000 and 4000 feet. The mirror 3261 is circumscribed by a lens set 3262. The lens set 3262 preferably comprises a plurality of relatively small positive lenses arrayed in a conical or hemispherical fashion. As the relatively small diameter first light beam 3140 reflects from the mirror 3261, the first light beam 3140 expands in diameter. The lens set 3262 re-collimates the expanding first light beam 3140 back to a slightly converging first light beam 3140 for atmospheric transmission to the subscriber transceiver units 3130. Conversely, the lens set 3262 focuses the second light beam 3150 from the subscriber transceiver units 3130 onto the mirror 3261. An aperture is formed in the lens set 3262 through which the relatively small diameter first and second light beams travel between the X-Y beam deflector 3240 and the mirror 3261. The mirror 3261 and lens set 3262 collimate beam 3150 in a manner optimized for the optical router 3261 access area.

By employing optical components to converge and re-collimate the light beams as described previously, the internal components of the optical router 3110, such as the beam deflector, advantageously operate on relatively narrow light beams. This improves the accuracy of beam redirection. Conversely, by employing optical components to expand and re-collimate the light beams as described previously, the light beams traveling through the atmosphere between network elements are advantageously relatively wide light beams. This improves the reception characteristics of the light beams as they are received by the receivers of the network components.

The optical router 3110 further comprises a receiver 3370 and a beam separator 3380. Preferably, the optical router 3110 establishes a control channel between the primary transceiver unit 3120 and the optical router 3110 for use in communicating control information, as previously discussed, from the primary transceiver unit 3120 to the optical router 3110. The control channel is distinct from the subscriber channels. Preferably, the beam deflector control system 3340 controls the beam deflector 3240 to redirect a particular first light beam 3140 to the beam separator 3380 rather than to the subscriber transceiver units 3130. This redirection to the beam separator 3380 rather than to the subscriber units 3130 preferably occurs at preset periods of time. The beam separator 3380 redirects the particular first light beam 3140 to the receiver 3370, which receives the first light beam 3140. The primary transceiver unit 3120 correspondingly modulates the control information data on the first light beam 3140 to be received and demodulated by the beam demodulator 3372 in the receiver 3370. The receiver 3370 is coupled to the beam deflector control system 3340 and communicates the control information data to the beam deflector control system 3340. The beam demodulator 3372 preferably comprises a photo-diode as is common in the art.

Preferably, the control channel is established in a time-multiplexed manner. During a time period, which is distinct from time periods devoted to subscriber channels, the beam control system 3340 controls the beam deflector 3240 to deflect the first light beam 3140 to a location on the mirror 3261 such that the first light beam 3140 is reflected to the beam separator 3380 rather than to the subscriber transceiver units 3130. The primary transceiver unit 3120 instructs the optical router 3110 to establish this control channel prior to the time for the optical router 3110 to establish the control channel. Preferably, during initialization, the optical router 3110 devotes all communication channels to be control channels until instructed by the primary transceiver unit 3120 to allocate subscriber channels.

In an alternate embodiment, the control channel is established in a frequency-multiplexed manner wherein a light beam of a distinct frequency, which is distinct from frequencies devoted to subscriber channels, is devoted to control channels.

The optical router 3110 further comprises an active optics control system 3350, such as are well known, particularly in the defense industry. The active optics control system 3350 provides stabilization of the first light beam 3140 on the optical antenna 3210 of the optical router 3110 and the second light beam 3150 on the optical antenna 3710 (of FIG. 8) of the primary transceiver unit 3120. As the first light beam 3140 travels from the optical antenna 3210 to the beam deflector 3240, a small portion of the first light beam 3140 is split by a beam splitter 3230 and redirected to a beam alignment detector 3352. The beam alignment detector 3352 detects misalignment or wander in the first light beam 3140 which may occur and stores the beam stabilization information. Atmospheric turbulence and density variations along the atmospheric path between the primary transceiver unit 3120 and the optical 3110 may account for misalignment of the first light beam 3140 on the optical router 3110. Likewise, events such as ground shifting or tower sway may cause the positions of the primary transceiver unit 3120 or optical router 3110 relative to each other to change.

The active optics control system 3350 communicates the beam stabilization information to the primary transceiver unit 3120 on a control channel. The primary transceiver unit 3120 uses the beam stabilization information to make corrections and stabilize the first light beam 3140 on the optical router 3110.

The optical router 3110 further comprises a transmitter 3360 including a light source 3362 and a beam modulator 3364. The active optics control system 3350 provides the beam stabilization information of the first light beam 3140 to the transmitter 3360. The light source 3362 generates and atmospherically transmits a control light beam 3250. The beam modulator 3364 modulates the positional information on the control light beam 3250 as it travels through the beam separator 3380 to the mirror 3261. Thus a control channel is established between the optical router 3110 and the primary transceiver unit 3120, similar to the control channel described above in which the primary transceiver unit 3120 transmits control information to the optical router 3110, but in the opposite direction. That is, while the beam deflector 3240 is controlled to deflect the first light beam 3140 to the mirror 3261 such that the mirror 3261 reflects the first light beam 3140 to the receiver 3370, the beam deflector 3240 also deflects the control light beam 3250 from the mirror 3261 to the optical antenna 3210. This provides a two-way or bi-directional control channel.

The optical router 3110 light source 3362 preferably comprises one or more continuous wave or pulsed beam lasers as are well known in the art, such as gas, solid state or diode lasers. The beam modulator 3364 preferably comprises an electro-optic cell. Alternatively, the beam modulator 3364 is a bulk type modulator. The light source and beam modulator configuration is indicative of those well known in fiber optic communication link transmission systems. However, the laser power output is typically significantly greater than those used in fiber optic systems.

Additionally, the active optics control system 3350 uses the beam misalignment information to control the beam adjuster 3220 to adjust the first light beam 3140 optimally into the beam deflector 3240.

As previously mentioned the primary transceiver unit 3120 communicates control information to the optical router 3110. The control information further comprises beam stabilization information which the optical router 3110 receives on the control channels. The active optics control system 3350 of the optical router 3110 uses the beam stabilization information from the primary transceiver unit 3120 to control the optical antenna 3210 and beam adjuster 3220 to make corrections and stabilize the second light beam 3150 on the primary transceiver unit 3120.

In an alternate embodiment, the optical router active optics control system 3350 further comprises a second beam alignment detector (not shown) which detects misalignment or wander in the second light beam 3150 from the subscriber transceiver units 3130 and stores the beam stabilization information. The optical router 3110 communicates the beam stabilization information to the primary transceiver unit 3120. The primary transceiver unit 3120 in turn communicates the beam stabilization information to the subscriber transceiver units 3130. The active optics control systems in the subscriber transceiver units 3130, discussed below, use the beam stabilization information from the primary transceiver unit 3120 to control the subscriber transceiver unit optical antennas and beam adjusters to make corrections for misalignment or wander and stabilize the second light beam 3150 on the optical router 3110.

In one embodiment the beam separator 3380 is a dichroic mirror. In another embodiment, the first light beam 3140 and second light beam 3150 are orthogonally polarized and the beam separator 3380 is a polarization separator.

Preferably, the optical router 3110 periodically polls the subscriber transceiver units 3130 by allocating a communication channel to each of the subscriber transceiver units 3130 within the range of accessibility of the optical router 3110. However, the optical router 3110 may lose reception of the second light beam 3150 from a given subscriber transceiver unit for a significant period of time. The most common cause of the reception loss is the subscriber transceiver unit being powered off. When the optical router 3110 detects reception loss, the optical router 3110 preferably and advantageously polls the powered-off subscriber less frequently than subscriber transceiver units which are actively transmitting a second light beam 3150 to the optical router 3110.

The Primary Transceiver Unit

Referring now to FIG. 8, the preferred embodiment of the primary transceiver unit 3120 in the network 3100 (of FIG. 1) is shown. The primary transceiver unit 3120 comprises an optical antenna 3710 optically coupled to a transmitter 3750 and a receiver 3770.

The optical antenna 3710 transmits the first light beam 3140 to the optical router 3110 (of FIG. 1) and receives the fourth light beam 3150 from the optical router 3110. (It is noted that for the network 3100 where the alternate embodiment of the optical router 3110 is employed, i.e., the network of FIG. 3, the optical antenna 3710 receives the second light beam 3150.) The optical antenna 3710 preferably is similar to the optical antenna 3210 of the optical router 3110. An optical antenna 3710 of the primary transceiver unit 3120 is contemplated with different dimensions and optical characteristics than the optical antenna 3210 of the optical router 3110.

The optical antenna 3710 of the primary transceiver unit 3120 is preferably larger than the subscriber transceiver unit optical antenna. Preferably, the receiver 3770 of the primary transceiver unit 3120 is more sensitive, i.e., able to demodulate a weaker light beam, than that of the subscriber transceiver units. Thus the subscriber transceiver unit light source, discussed below, may be less powerful, thus reducing the cost of the subscriber transceiver units. In other words, the primary transceiver unit 3120 transmitter light source 3754 is preferably more powerful than the subscriber transceiver unit light source. This allows the subscriber transceiver unit antenna, discussed below, to be relatively small and the subscriber transceiver unit receiver, discussed below, to be relatively less sensitive. Hence the total cost of the system is reduced since the number of subscriber transceiver units is typically much greater than the number of primary transceiver units in the network.

A data source/sink (not shown) provides data to the primary transceiver unit 3120 to be sent to the subscriber transceiver units 3130. The data source/sink ties into and/or uses existing communication structures such as a telephone network, cable television system, the Internet or other networks employing Asynchronous Transfer Mode (ATM), switched-ethernet, SONNET, FDDI, Fibre-Channel, Serial Digital Heirarchy, etc. Various means for coupling the data source/sink to the primary transceiver unit 3120 are contemplated, such as fiber-optic cable, satellite up-links and down-links, atmospheric light beams, coaxial cable, microwave links, etc. The light source 3754 generates and atmospherically transmits the first light beam 3140 upon which the beam modulator 3752 modulates the data to be sent to the subscriber transceiver units 3130. A beam adjuster 3720, which preferably comprises an adjustable fine steering mirror, receives and reflects the first light beam 3140 to a lens assembly 3780 and optical antenna 3710 which expand, re-collimate and transmit the first light beam 3140 to the optical router 3110.

Conversely, the primary transceiver unit optical antenna 3710 atmospherically receives the fourth light beam 3150 from the optical router 3110, and the lens assembly 3780 focuses the fourth light beam 3150 onto the beam adjuster 3720. The beam adjuster 3720 reflects the narrowed fourth light beam 3150 to a beam separator 3740. The beam separator 3740 is similar to that of the optical router 3110. The beam separator 3740 redirects the fourth light beam 3150 to the receiver 3770. The beam demodulator 3772 receives the fourth light beam 3150 and demodulates the data sent by the subscriber transceiver units 3130. The data is then provided to the data source/sink. The beam demodulator 3772 preferably comprises a photo-diode, as is common in the art.

The primary transceiver unit light source 3754 preferably comprises one or more continuous wave or pulsed beam lasers as are well known in the art, such as gas, solid state or diode lasers. The beam modulator 3752 preferably comprises an electro-optic cell. Alternatively, the beam modulator 3752 is a bulk type modulator. The light source and beam modulator configuration is similar to those well known in fiber optic communication link transmission systems. However, the laser power output is typically significantly greater than those used in fiber optic systems.

The light beam wavelengths generated by the atmospherically transmitting light sources described in the present invention are chosen to minimize the power loss through the atmosphere. Preferably the wavelengths are in the near infrared range.

The lens assembly 3780 and optical antenna 3710 are configured to transmit the first light beam 3140 having a beam waist which is advantageously located at the optical router 3110. The diameter of the first light beam 3140 leaving the optical antenna 3710 is many times the diameter of the first light beam 3140 exiting the light source 3754. Thus the laser power density is spread over a relatively large, cross-sectional area, which enhances eye-safety. Additionally, the relatively large diameter of the light beams traveling between the components of the network improves the reception characteristics of the light beams at the optical receivers.

The primary transceiver unit 3120 additionally comprises a control system (not shown) which computes the previously discussed routing, beam stabilization, timing, subscriber location and multiplexing control information.

The primary transceiver unit 3120 further comprises an active optics control system 3760 similar to the active optics control system 3350 of the optical router 3110. The primary transceiver unit active optics control system 3760 cooperates with the optical router active optics control system 3350 to provide stabilization of the first light beam 3140 on the optical antenna 3210 of the optical router 3110 and the fourth light beam 3150 on the optical antenna 3710 of the primary transceiver unit 3120.

As previously mentioned, the optical router 3110 communicates beam stabilization information to the primary transceiver unit 3120. The active optics control system 3760 uses the beam stabilization information from the optical router 3110 to control the optical antenna 3710 and beam adjuster 3720 to make corrections and stabilize the first light beam 3140 on the optical router 3110.

Additionally, the active optics control system 3760 uses the beam misalignment information detected by the beam alignment detector 3762 to control the beam adjuster 3720 to adjust the fourth light beam 3150 optimally into the receiver 3770.

The Subscriber Transceiver Units

Referring now to FIG. 9, an illustration of the preferred embodiment of a subscriber transceiver unit 3130A in the network 3100 (of FIG. 1) is shown. Subscriber transceiver unit 3130A is representative of the plurality of subscriber transceiver units 3130. The subscriber transceiver unit 3130A comprises an optical antenna 3510 coupled to an input/output device 3600, such as a set-top box 3600, by a fiber optic cable 3590. The input/output device 3600 may be any of various devices, including a set-top box, computer system, television, radio, teleconferencing equipment, telephone or others which may be coupled to the optical antenna 3510 by a fiber optic cable 3590. In the remainder of this disclosure, the input/output device 3600 is referred to as a set top box. Power and control wires (not shown) also couple the subscriber optical antenna 3510 and the set-top box 3600.

The optical antenna 3510 receives the second light beam 3845 from the optical router 3110 (of FIG. 1) and transmits the third light beam 3855 to the optical router 3110. (It is noted that for the network 3100 where the alternate embodiment of the optical router 3110 is employed, i.e., the network of FIG. 3, the subscriber transceiver unit 3130A receives the first light beam 3140 from the optical router 3110 and transmits the second light beam 3150 to the optical router 3110.) The optical antenna 3510 preferably is similar to the optical antenna 3210 of the optical router 3110. An optical antenna 3510 of the subscriber transceiver unit 3130A is contemplated with different dimensions and optical characteristics than the optical antenna 3210 of the optical router 3110.

The optical antenna 3510 receives the second light beam 3845 and focuses the second light beam 3845 into a fiber-optic coupling 3580. The fiber-optic coupling 3580 couples the second light beam 3845 into the fiber optic cable 3590. The fiber optic cable 3590 carries the second light beam 3845 to the set-top box 3600. A beam separator 3570 in the set-top box 3600 redirects the second light beam 3845 to a receiver 3550 which receives the second light beam 3845. A beam demodulator 3552 in the receiver 3550 demodulates the data from the second light beam 3845. The receiver 3550 provides the data to external connections (not shown) on the set-top box 3600, which connect to various devices such as televisions, computers, radios, teleconferencing equipment and telephones (also not shown). The beam demodulator 3552 preferably comprises a photo-diode as is common in the art.

Conversely, the various digital devices provide data to be sent to the primary transceiver unit 3120 (of FIG. 1) to a transmitter 3560 in the set-top box 3600. The set-top box 3600 comprises a light source 3564 which generates the third light beam 3855. A beam modulator 3562 in the transmitter 3560 modulates the data to be sent to the primary transceiver unit 3120 on the third light beam 3855. The third light beam 3855 passes through the fiber optic cable 3590 to the fiber-optic coupling 3580. The fiber optic coupling 3580 decouples the third light beam 3855 from the fiber optic cable 3590 and atmospherically redirects the third light beam 3855 to the optical antenna 3510. The optical antenna 3510 then transmits the third light beam 3855 including the data to the optical router 3110.

The subscriber transceiver unit 3130A light source 3564 preferably comprises one or more continuous wave or pulsed beam lasers as are well known in the art, such as gas, solid state or diode lasers. The beam modulator 3562 preferably comprises an electro-optic cell. Alternatively, the beam modulator 3562 is a bulk type modulator. The light source and beam modulator configuration is similar to those well known in fiber optic communication link transmission systems. However, the laser power output is typically greater than those used in fiber optic systems.

In an alternate embodiment, previously mentioned, the subscriber transceiver unit 3130A is configured to transmit and receive multiple wavelength light beams in order to increase the data bandwidth available to a given subscriber.

The subscriber transceiver unit 3130A further comprises an active optics control system 3540 similar to the active optics control system of the optical router 3110 and the primary transceiver unit 3120. The subscriber transceiver unit active optics control system 3540 cooperates with the primary transceiver unit 3120 active optics control system to provide stabilization of the second light beam 3845 on the subscriber transceiver unit 3130A and the third light beam 3855 on the optical router 3110.

A beam alignment detector 3542 detects misalignment or wander in the second light beam 3845 from the optical router 3110 and stores the beam stabilization information. The subscriber transceiver unit 3130A communicates the beam stabilization information regarding the first light beam 3150 to the primary transceiver unit 3120 via the transmitter 3560. The invention contemplates the beam stabilization information being communicated to the primary transceiver unit 3120 in a header in a subscriber data packet. The invention additionally contemplates the beam stabilization information being communicated to the primary transceiver unit 3120 via a dedicated control data packet. The primary transceiver unit 3120 utilizes the beam stabilization information when computing positional and multiplexing control information.

A beam adjuster 3520 optically positioned between the optical antenna 3510 and the fiber optic coupling 3580 is controlled by the active optics control system 3540 to maintain efficient coupling of the second light beam 3845 into the fiber optic cable 3590.

The optical antenna 3510 is mounted on gimbals (not shown) which allow the optical antenna 3510 to rotate and search for an optical router 3110, or different transceiver module 3800 of the preferred optical router 3110, by which to receive service upon installation or upon loss of reception from a current optical router 3110 or transceiver module 3800.

Alternate Embodiments

An alternate embodiment of the subscriber transceiver unit 3130A is contemplated in which the light beams are converted to/from electrical signals at the optical antenna 3510 and transmitted in electronic form to the input/output device 3600. Hence, alternative transmission mediums for coupling the optical antenna 3510 to the input/output device 3600 are contemplated such as coaxial cable or other forms of electrical wires.

Referring now to FIG. 10, an alternate embodiment of the set-top box 3600 of FIG. 9 is shown. A fiber optic “T” 4020 is coupled to the fiber optic cable 3590. The second light beam 3845 enters the fiber optic “T” 4020 and passes along the fiber optic cable 3590 to a beam demodulator 4030. The beam demodulator 4030 is similar to and performs similar functions to the beam demodulator 3552 of the preferred embodiment. The second light beam 3845 then passes through the fiber optic cable 3590 to an optical data remover 4040. The optical data remover 4040 preferably comprises a micro-bender. The data remover 4040 removes any data which has been modulated on the second light beam 3845. At this point the second light beam 3845 essentially becomes the third light beam 3855. The third light beam 3855 is then passed along the fiber optic cable 3590 to a beam modulator 4050. The beam modulator 4050 is similar to and performs similar functions to the beam modulator 3562 of the preferred embodiment of the subscriber transceiver unit 3130A. The third light beam 3855 including the second data is then passed to the fiber optic “T” 4020 and on to the fiber optic coupling for transmission to the optical router 3110. The alternate embodiment advantageously avoids the cost of a light source.

An alternate embodiment of the subscriber transceiver unit 3130A optical antenna is contemplated in which the antenna is an omni-directional antenna. The omni-directional antenna is similar to the mirror and lens set assembly of the alternate embodiment of the optical router 3110. Additionally, a beam deflector is provided for coupling and decoupling the light beams into and out of the fiber optic coupling 3580. Alternatively, the fiber optic coupling 3580 is rotatably mounted. The alternate embodiment advantageously enables the subscriber unit 3130 to receive service from an alternate optical router 3110 with minimal interruption of data transmission. In addition, installation of the subscriber transceiver unit 3130 is simplified in that virtually no alignment must be performed upon installation, other than achieving a line of sight path to one or more optical routers 3110.

The present invention contemplates the use of fiber optic amplifiers, such as an EDFA (erbium-doped fiber amplifier), in one or more of the various network elements for amplifying the various ligth beams in order to achieve appropriate signal power levels of the various light beams within the network. Thus, as shown in the embodiments of network 3100 illustrated in FIG. 1 and 3, network elements such as optical router 3110, primary transceiver unit 3120 and the subscriber transceiver units 3130A–N may include EDF As 3111, 3121 and 3131A–N respectively.

The present invention contemplates the use of atomic line filters, which act as optical band-pass filters for selected light wavelengths, in one or more of the various network element receivers for filtering out necessary light wavelengths, such as sunlight.

The present invention contemplates the use of light sources in the various network element transmitters with adjustable light beam power control. The light beam power is adjusted according to factors such as weather conditions to achieve a proper fade margin for the signal power. A fade margin of 15 dB at a 1 km range to achieve a 10⁻⁹ bit error rate is preferred.

Conclusion

Therefore, the present invention comprises a wireless point-to-multipoint wide area telecommunications network by establishing subscriber communications channels in a multiplexed manner using atmospherically transmitted light beams. The network employs an optical router to establish the communications channels between a primary transceiver unit and a plurality of subscriber transceiver units by time-multiplexing, light beam frequency multiplexing, or a combination thereof, the atmospherically transmitted light beams.

Although the systems and networks of the present invention have been described in connection with several preferred embodiments, the present invention is not intended to be limited to the specific forms set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the invention as defined by the appended claims. 

1. A terrestrial optical communication network comprising: a plurality of fiber optic links and free-space links between which optical signals are optically coupled by erbium doped fiber amplifiers (EDFAs), wherein a power gain of at least one of the EDFAs is operable to be controlled in response to one or more factors; at least one optical router connected to a plurality of links, wherein the optical router includes one or more EDFAs to optically couple the optical signals from one of the links connected to the optical router to another one of the links connected to the optical router.
 2. A terrestrial optical communication network as defined in claim 1 wherein the one or more factors comprise weather conditions.
 3. A terrestrial optical communication network as defined in claim 1 wherein the one or more factors comprise an optical signal received over one of the free-space links.
 4. A terrestrial optical communication network as defined in claim 1, further comprising a control system for controlling the power gain of at least one of the EDFAs.
 5. A terrestrial optical communication network as defined in claim 4, wherein the control system is an active optics control system.
 6. A terrestrial optical communication network as defined in claim 1, wherein the EDFAs include a transmitting EDFA, wherein the transmitting EDFA amplifies one of the optical signals before its transmission over at least one of the free-space links, and further comprising a controller connected to the transmitting EDFA to control the optical power gain of the transmitting EDFA to adjust the optical power of the optical signal transmitted over the one free-space link.
 7. A terrestrial optical communication network as defined in claim 1, wherein the EDFAs include a receiving EDFA, wherein the receiving EDFA amplifies one of the optical signals after its reception over at least one of the free-space links, and further comprising a controller connected to the receiving EDFA to control the optical power gain of the receiving EDFA to adjust the optical power of the optical signal delivered by the receiving EDFA.
 8. A terrestrial optical communication network comprising; a plurality of network elements coupled together by a plurality of fiber optic links and free-space links, wherein the terrestrial optical communication network further comprises one or more erbium doped fiber amplifiers (EDFA) in one or more of the network elements for amplifying light beams in the network in order to achieve appropriate signal power levels of the light beams within the network; at least one optical router connected to a plurality of links, wherein the optical router includes one or more EDFAs to optically couple the optical signals from one of the links connected to the optical router to another one of the links connected to the optical router.
 9. A terrestrial optical communication network as defined in claim 8, wherein the one or more EDFAs are operable to provide adjustable light beam power control according to one or more factors.
 10. A terrestrial optical communication network as defined in claim 9 wherein the one or more factors comprise weather conditions.
 11. A terrestrial optical communication network as defined in claim 9 wherein the one or more factors comprise an optical signal received over one of the free-space links.
 12. A terrestrial optical communication network as defined in claim 8, further comprising a control system for controlling the power gain of at least one of the EDFAs.
 13. A terrestrial optical communication network as defined in claim 8, wherein the EDFAs include a transmitting EDFA, wherein the transmitting EDFA amplifies one of the optical signals before its transmission over at least one of the free-space links, and further comprising a controller connected to the transmitting EDFA to control the optical power gain of the transmitting EDFA to adjust the optical power of the optical signal transmitted over the one free-space link.
 14. A terrestrial optical communication network as defined in claim 8, wherein the EDFAs include a receiving EDFA, wherein the receiving EDFA amplifies one of the optical signals after its reception over at least one of the free-space links, and further comprising a controller connected to the receiving EDFA to control the optical power gain of the receiving EDFA to adjust the optical power of the optical signal delivered by the receiving EDFA.
 15. A terrestrial optical communication network comprising: a plurality of network elements; a plurality of fiber optic links and free-space links for coupling the plurality of network elements through transfer of light beams; and one or more erbium doped fiber amplifiers (EDFA) for amplifying the light beams in the network in order to achieve appropriate signal power levels of the light beams within the network; wherein the plurality of network elements comprises at least one optical router connected to a plurality of the links, wherein the optical router includes one or more EDFAs to optically couple the optical signals from one of the links connected to the optical router to another one of the links connected to the optical router. 